THE PAL.EONTOLOGICAL RECORD 123

legend of the Tower of Babel «does not seem ever to
have been as seriously believed in as the legend of the
four days' creation of living things. As a boy, how-
ever, I remember being told by an educated Welshman
that English was not a language, as Welsh was : it was
only a " speech." I understood him to mean that
Welsh was created ready-made in the year B.C. 2247,
while English had been naturally evolved at a later
date. The difference between "language" and
"speech" corresponded to that drawn by Linnaeus
between "species" and "variety," or by Dewar be-
tween " family " and "genus."

Why should cases such as are cited under the first
heading above be so few in number, if evolution is
universal ? For a very simple reason. Such lines can
only be traced completely and certainly when the whole
evolution takes places within a single area of con-
tinuous sedimentation, so that successive fc mutations "
(in the palseontological or Waagenian sense of the term)
are preserved in successive strata. But that implies
conditions of life that remain constant, or change very
slowly. Consequently the evolution itself may be very,
slow. This increases the chance of preservation of a
complete record, but gives a wrong idea of the rate at
which evolution can take place. A very good example
is the evolution of the genus Micraster in the White
Chalk. This deposit accumulated in the course of a
long period of time during which, over a large area of
North-Western Europe, conditions remained almost
unchanged, except for a gradual deepening of the sea-
bottom (with one or two interruptions). Parallel evolu-
tion took place in Echinocorys and in several species